1. Field of the Invention
The present invention relates to a working vehicle comprising a pair of hydraulic pump units being separate to each other, a hydraulic pump set comprising a pair of hydraulic pump units arranged apart from each other, a hydraulic pump unit fluidly connected to a hydraulic actuator such as a hydraulic motor unit arranged spaced apart, and a hydraulic pump unit comprising a pump body and an auxiliary pump body driven by a pump shaft.
2. Related Art
There has been conventionally known to arrange an HST formed by a hydraulic pump unit and a hydraulic motor unit for each pair of driving wheels to independently speed-change drive each of the pair of driving wheels.
Particularly, in a working vehicle such as a riding mower tractor capable of performing zero turn, requiring a space between a pair of driving wheels in order to stabilize a vehicle position during turning, there has been proposed a configuration that first and second hydraulic motor units are distributed and arranged in the width direction of the vehicle so as to be positioned in the vicinity of the corresponding driving wheel (see, for example, U.S. Pat. No. 6,332,393, hereinafter referred to as a cited reference).
In the vehicle disclosed in the cited reference, first and second hydraulic pump units that form HSTs in cooperation with the first and second hydraulic motor units respectively, are independently attached to a vehicle frame.
Specifically, each of the first and second hydraulic pump units forms an independent unit with respect to the corresponding hydraulic motor units, and the first and second hydraulic pump units are arranged at an arbitrary position spaced apart from the first and second hydraulic motor units. The space between the first and second hydraulic pump units is utilized as a space for accommodating vehicle-mounted-components such as an oil tank and a battery.
As mentioned above, the degree of freedom of design of the vehicle can be improved by arranging the first and second hydraulic pump units independently. However, the conventional configuration does not sufficiently take into consideration an aspect of maximally utilizing the free space between the first and second hydraulic pump units.
That is, a drain port for returning a drain oil to an oil tank, and a charge suction port for sucking a charge oil from the oil tank must be provided in each of the first and second hydraulic pump units.
Therefore, in order to maximally utilize the free space between the first and second hydraulic pump units, conduits for such ports must be considered. However, in the conventional configuration, this aspect is not taken into consideration.
A first aspect of the present invention, in view of the conventional art, aims to provide a working vehicle in which first and second hydraulic pump units are distributed and arranged in the width direction of the vehicle and which is configured to effectively utilize a space between the first and second hydraulic pump units.
Further, there has been conventionally known to form a pair of HSTs by fluidly connecting between a pair of hydraulic pump units arranged apart from each other and a pair of driven side actuators such as hydraulic motor units arranged apart from each other.
This configuration is particularly effective in a working vehicle in which a space must be formed between a pair of driving wheels, like a center discharge-type mower tractor.
That is, in the working vehicle, by arranging a pair of hydraulic pump units spaced apart along the width direction of the vehicle and, also, arranging a pair of hydraulic motor units spaced apart along the width direction of the vehicle, a free space can be secured at the center in the width direction of the vehicle without enlarging the vehicle width.
Each of the pair of hydraulic pump units comprises a pump shaft operatively connected to a driving source, a pump body driven by the pump shaft, a port block supporting the pump body and formed with a supply/discharge oil passage for the pump body, and a pump case removably connected to the port block so as to accommodate the pump body.
For instance, the following proposals have been made in the cited reference in an aim to have the components of the pair of hydraulic pump units common.
That is, in the hydraulic pump unit disclosed in the cited reference, the port block is connectable to the pump case in both a state where the pump case is positioned at a first position about the pump shaft and a state where the pump case is positioned at a second position rotated by 180 degrees about the pump shaft from the first position.
The port block has an operating oil port provided on a first side in the front-to-rear direction of the vehicle and a drain port provided on both sides in the width direction of the vehicle.
Of the pair of port blocks in one port block connected to the pump case positioned at the first position, the drain port on one side in the width direction of the vehicle is closed by a plug. On the other hand, in the other port block, the drain port on the other side in the width direction of the vehicle is closed by the plug.
The pair of hydraulic pump units disclosed in the cited reference allow the components to be common and direct both drain ports toward the outside in the width direction of the vehicle, but have the following disadvantages.
That is, the port block and the pump case are connected by way of a connecting hole arranged on the same radius about the pump shaft.
In this configuration, there arises a possibility that both of the pair of pump cases connect to the corresponding port block at the first position during the assembling work of the hydraulic pump units.
Particularly, the hydraulic pump unit is assembled by a hydraulic equipment manufacturer and, then, is shipped to a vehicle manufacturer after being subjected to various adjustment works.
That is, in the hydraulic manufacturer, the hydraulic pump unit is not actually attached to the vehicle frame, but the port block and the pump case are assembled.
Therefore, the aforementioned assembling error likely occurs, and attention must be given to such assembly error thereby worsening the assembling work efficiency.
A second aspect of the present invention, in view of the conventional art, aims to provide a hydraulic pump set which comprises a pair of hydraulic pump units separate with respect to each other and which can prevent the assembling error while having the components as common as possible.
The second aspect of the present invention also aims to provide a hydraulic pump unit capable of changing the direction of an operating oil port without changing the relative position of a port block and a pump case.
Further, there has been utilized in various devices such as a working vehicle to arrange a hydraulic actuator such as a hydraulic motor and a hydraulic pump unit fluidly connected to the hydraulic actuator spaced apart from each other (see, for example, the cited reference).
This configuration is particularly effective in a working vehicle in which a space must be formed between a pair of driving wheels in order to stabilize the vehicle position during turn, such as a riding mower tractor capable of performing zero turn.
A device provided with the above hydraulic pump unit requires a configuration for replenishing an operating oil flowing between the hydraulic pump unit and the hydraulic actuator and, also, storing a drain oil from the hydraulic pump unit.
Regarding the above, the cited reference discloses an oil tank attached to a vehicle frame independent from the hydraulic pump unit.
However, the configuration disclosed in the cited reference requires the installation work of the oil tank aside from the installation work of the hydraulic pump unit, and the hydraulic pump unit and the oil tank must be connected with conduits after being installed; thus, there arises a disadvantage in terms of installation workability of the entire hydraulic pump unit.
A third aspect of the present invention, in view of the conventional art, aims to provide a hydraulic pump unit which comprises an oil tank for storing a drain oil from a pump body and acting as a charge oil source for the pump body, and is capable of eliminating the conduit connecting work and improving the installation working efficiency of the entire hydraulic pump unit including the oil tank.
As mentioned above, in the vehicle disclosed in the cited reference, the first and second hydraulic pump units in the pair of HSTs are arranged independently with respect to the corresponding hydraulic motor unit to improve the degree of freedom of design of the vehicle. However, a sufficient consideration is not made to replenishing the pressure oil to the pair of HSTs.
That is, in the conventional configuration, a dedicated charge pump unit is provided to each of the pair of hydraulic pump units.
With the above configuration, the charge pump unit itself must be prepared in pairs, and a hydraulic circuit such as a relief valve for setting the oil pressure of each charge line must also be prepared in pairs.
A fourth aspect of the invention, in view of the conventional art, aims to provide a hydraulic pump set which comprises first and second hydraulic pump units arranged apart from each other, and is capable of efficiently performing the replenishing of a pressure oil to the first and second hydraulic pump units at a low cost.
The fourth aspect of the present invention also aims to provide a hydraulic pump unit which efficiently performs the replenishing of a pressure oil to oneself in addition to supply of an operating oil to an external hydraulic device.
In the vehicle disclosed in the cited reference, the first and second hydraulic pump units configuring a pair of HSTs in cooperation with the first and second hydraulic motor units are independently attached to the vehicle frame.
Specifically, the first and second hydraulic pump units independently form a unit, and the first and second hydraulic pump unit are arranged at an arbitrary position spaced apart from the first and second hydraulic motor units.
The conventional configuration enables to improve the degree of freedom of the vehicle by independently arranging the first and second hydraulic pump units; however, a sufficient consideration is not made other than replenishing the pressure oil to the HST.
That is, in the working vehicle such as a mower tractor, various external hydraulic devices such as a hydraulic lift device is annexed. However, in the conventional configuration, only the charge pump unit is arranged in each of the pair of hydraulic pump units, and supplying the operating oil to the external hydraulic device is not considered.
A fifth aspect of the present invention, in view of the conventional art, aims to provide a hydraulic pump set which comprises first and second hydraulic pump units arranged apart from each other, and is capable of efficiently performing replenishing of a pressure oil to the first and second hydraulic pump units and, also, efficiently performing supply of an operating oil to an external hydraulic device.
The fifth aspect of the present invention also aims to provide a hydraulic pump set which can efficiently perform the replenishing of the pressure oil to oneself in addition to supply of the operating oil to the external hydraulic device.
As mentioned above, the cited reference discloses a configuration that the hydraulic actuator such as a hydraulic motor and the hydraulic pump unit fluidly connected to the hydraulic actuator are arranged apart from each other.
Specifically, the cited reference discloses, as one example of the independent-type hydraulic pump unit, a hydraulic pump unit comprising a pump shaft operatively connected to a driving source, a pump body rotatably driven by the pump shaft, a pump case for accommodating the pump body, a port block connected to the pump case while supporting the pump body, and an auxiliary pump body driven by the pump shaft.
The conventional hydraulic pump unit eliminates an additional transmission mechanism from the driving source to the auxiliary pump body by being configured so as to rotatably drive the auxiliary pump body using the pump shaft rotatably driving the pump body, but still needs improvement in the following points.
That is, the conventional hydraulic pump unit has an operating oil port serving as an operating fluid connecting port to the actuator, a suction port serving as a fluid draw-in port to the auxiliary pump body, and a drain port for drawing out the drain oil from the pump body, which are all formed in the port block.
Therefore, the oil passage configuration in the port block is complicated.
A sixth aspect of the present invention, in view of the conventional art, aims to provide a hydraulic pump unit which comprises a pump body and an auxiliary pump body driven by the pump shaft, and is capable of satisfactorily forming a fluid connecting port to the outside.